Little panaque soon to be TITAN?

[MatsP]

Actually Donovan tested both live and dead fish.

See the section called "Fiber digestion" in this.

--
Mats

[dw1305]

Hi all,
I had some correspondence with Donovan German about his "xylophagous Plec" work. I found it very interesting, because intuitively you would suspect that if teeth like that had evolved, some adaptation to the gut would have occurred as well. Dr German wasn't sure why the gut was so un-specialised compared to their teeth, but thought it was probably that the genetic potential existed to allow the teeth to evolve, but that the gut DNA didn't possess the necessary variability.

He started the work from the premise that Panaque spp. would be a good source of novel wood degrading organisms (he was really interested in these rather than the fish), so the findings were a great disappointment to him.

An analogy would be the Giant Panda, which has evolved an enlarged wrist bone based "false thumb" to allow it to grasp the Bamboo it feeds on, but retains the gut of its carnivorous ancestors which stops it effectively digesting it. The Giant Panda survives because it is surrounded by Bamboo and can eat for 23 hours a day, presumably in the same way that a Panaque is surrounded by the wood it feeds on, but cannot digest. Another point of interest was that Donovan observed the Panaques feeding on a wide range of woody debris.

It was a long correspondence with lots of detail, but he did include a summary of his work.

Dr Germans summary:

"So, just to summarize what I think these fish are doing… the wood-eating catfishes dig into decaying wood and efficiently digest wood degradation products that environmental microbes are making available as they degrade wood. The fish also have elevated digestive enzyme activities (e.g., N-acetyl-b-D-glucosaminidase) suggestive that they digest fungi within the wood matrix. Thus, they likely get “energy” from the degraded wood. The stable isotopic signatures (carbon and nitrogen) of wild-caught wood-eating catfishes certainly suggest that they get their protein from fungi and amorphous detritus, and we find periphyton and amorphous detritus in their guts (in addition to the wood; see the “inside the guts” paper where I do a detailed gut content analysis of wild-caught fish). Basically, the fish have to get their nitrogen from somewhere other than the wood detritus (there isn’t much N in wood anyway). The fish certainly ingest wood, they just don’t use the same “pathway” to obtain energy from it as a termite. Rather than harbouring an endosymbiotic community, they let the microbes in the environment do the work for them. This may be a function of living in an aquatic environment."

cheers Darrel

[Jools]

A rather unscientific observation from me, but my young dwarf Panaque (home bred) grow faster on dead collected bogwood (without bark) than on fresh wood with (beech, privet hedge, apple) despite stripping the bark in under a fortnight. I was surprised at this thinking fresher would be better. Roughly equal sawdust laden poo is produced. I guess that micro-organisms in the top 2mm of dead wood are where these fishes are getting the most benefit, but they get less from fresh wood. Or it's harder to get at.

Either way, unless you are supplementing it with something better, dead wood is best. That said, I think quite a lot of dead wood you encounter in an LFS is fairly much "nutrition neutral". Most of my "dead wood" has been lying in a river, pond or lake for some time.

Jools

[MatsP]

Jools,

I agree, my Panaque spp. seem to prefer the wood that is old in the tank, and pieces that I've bought on auction that are "used" are better than the ones that come from the LFS, from what I can tell. And at although unscientific, I think it reflects the proposed theory in Donovan's work... Older wood will have more "stuff living in it", thus better for Panaque...

--
Mats

[nvcichlids]

I have had similar findings with one that I found very interesting. I decided to bring a piece of wood home from a local river this summer. it was covered with aquatic moss (like 1/2" thick of moss!) and then I also brought home some typical.. "Older" wood that I knew they would like. My panaque destroyed the moss and that piece of wood prior to touching anything else (well they may have touched other pieces, but I could always find them somewhere on this piece of wood when I did my daily fish count.)

Is is possible that the moss had more "living stuff" under it than even the normal wood.

[taksan]

This is certainly true, New wood is nutritionally useless for Panaques but old wood with various organisms and fungi, moss, algae attached is what they are after. We cannot provide old wood as a constant source which is why I came up with the paste. It gets into the wood and they chew through it. The wood is just the bread ...in the wild they are after the butter. In a tank we have to provide the butter.

[dw1305]

Hi all,
Yes, as the quote shows Donovan was pretty sure that the Panaques were assimilating the nutrients from fungi within the wood. This wouldn't be that surprising as the Basidiomycota (the "white rotting" Bracket fungi etc) have the ability to preferentially degrade lignin.

The fish also have elevated digestive enzyme activities (e.g., N-acetyl-b-D-glucosaminidase) suggestive that they digest fungi within the wood matrix. Thus, they likely get “energy” from the degraded wood. The stable isotopic signatures (carbon and nitrogen) of wild-caught wood-eating catfishes certainly suggest that they get their protein from fungi .....

If I was keeping Panaques I'd keep the structural wood in, but also feed small amounts of rotted wood, you could literally collect any fallen non-coniferous wood, and pile it up in a damp corner of the garden, once it's started to break down and you can see the fungal mycelia transfer it in to the tank. So really just treat it like another "vegetable", and if neccesary take it out before it effects water quality.

A thought occurs that you could culture Oyster mushrooms, Shiitake etc on a Birch log, and feed the spent logs to your fish. <http://www.ragmans.co.uk/produce/mushroom_logs/>

cheers Darrel

[MatsP]

Or even better, befriend a local mushroom growing-place and ask if you can have the old logs? ;)

--
Mats

[dw1305]

Hi all,

Or even better, befriend a local mushroom growing-place and ask if you can have the old logs?

Now there is a good idea. My suspicion would be that for commercial production of Pleurotus they don't always use logs, but compressed straw or saw-dust or possibly even some form of woody waste from the paper industry. I'll have a look into this and see what I can find.

If you are collecting your own wood, it should be pretty easy to find appropriate fungally rotted wood, it will be soft due to the loss of structural lignin and white due to the hyphae of the fungi. Unsurprisingly it will also smell of "mushrooms". The only question would then be would the fish recognise it and preferentially feed on it? or are they undiscriminating feeders who just process whatever wood is to hand?

Hard wood sawdust or cereal straw might be a good medium for rapid hyphal production and you may be able to turn this into a fungal Panaque pellet or frozen cube.
Something like this perhaps? <http://www.seedsofitaly.com/product/596>

I haven't got any Panaques but does some-one else want to have a go and see how they get on?

cheers Darrel